Bosentan

How it works

It blocks endothelin-1 at both ETA and ETB receptors, counteracting the vasoconstriction and vascular remodelling that drive raised pulmonary arterial pressure.

Prescribing in practice

• Most important: it is hepatotoxic and teratogenic, so liver function must be checked before and monthly during treatment and effective contraception is mandatory, with hormonal contraception alone being unreliable because bosentan induces its metabolism.
• It can cause dose-related anaemia, so check haemoglobin before and during therapy.
• Numerous interactions arise from its enzyme induction and the contraindication with ciclosporin and glibenclamide; review concomitant drugs carefully.

Monitoring

Monitor monthly liver transaminases, periodic haemoglobin, blood pressure, and pregnancy status in those of childbearing potential.

Counselling the patient

• Use reliable non-hormonal or additional barrier contraception and report a missed period immediately.
• Report unusual tiredness, nausea, dark urine, or jaundice, which may indicate liver problems.

Evidence & guidelines

Bosentan's benefit in pulmonary arterial hypertension is established by randomised trials showing improved exercise capacity, reflected in ESC/ERS guidance.